This invention relates to a unique way of mounting the non-orbiting scroll such that it is not pinched.
Scroll compressors have been becoming widely utilized in refrigerant compression applications. In the scroll compressor, a pair of scroll members each have a base and a generally spiral wrap extending from the base. The wraps interfit to define compression chambers. One of the two scroll members is caused to orbit relative to the other, and as the two orbit the size of the compression chambers is reduced. An entrapped refrigerant is compressed and discharged through a discharge port.
During this compression, a force is created from the entrapped refrigerant tending to force the two scroll members away from each other. If the two scroll members move away from each other, then the compression chambers are no longer sealed, and adequate compression may not occur. Thus, it is typical to provide a force behind one of the two scroll members biasing that one scroll member towards the other. The other scroll member is typically axially fixed. In one type of scroll compressor, the back pressure chamber which creates the resisting force is placed behind the orbiting scroll. In such a scroll compressor the non-orbiting scroll is typically axially fixed. Typically, a housing member is crimped onto the non-orbiting scroll to lock it against movement. Some problems are created with this construction in that the crimping force may cause deformation in the non-orbiting scroll, and further puts design requirements on the non-orbiting scroll.
Further, the non-orbiting scroll is often welded to the housing. The weld joint further creates the potential for damage, and further complicates the design considerations.
In disclosed embodiments of this invention, a non-orbiting scroll member is secured against axial movement without being secured to any of the housing members. In this way, the challenges raised by the crimping force in the prior art are eliminated.
In one embodiment, the non-orbiting scroll has a seal at its outer periphery that seals on the inner periphery of an end cap. A spring biases a non-orbiting scroll back towards the orbiting scroll. The back pressure chamber is provided behind the orbiting scroll. At startup of the scroll compressor, there is little force behind the non-orbiting scroll holding it toward the orbiting scroll. However, the spring will hold the two scroll members in contact until compression begins, and the pressure behind the orbiting scroll builds up. At steady state operation the discharge pressure in a chamber behind the non-orbiting scroll will hold it against the orbiting scroll.
One further advantage of this embodiment is that in the event the scroll members begin to rotate in a reverse direction, which is an undesirable event that does sometimes occur, a vacuum is created in the nominal discharge chamber, and overcomes the spring force and allow the two scroll members to move out of contact with each other. This will reduce or prevent damage to the scroll members and the remainder of the compressor.
In a second embodiment the non-orbiting scroll is force fit into an end cap. The force fit is designed to have sufficient force such that it can resist the separating force from the entrapped gas until the discharge pressure can build up. In a further modification of this basic embodiment, a tube is placed between the rear of the non-orbiting scroll and the end cap to further secure the non-orbiting scroll in place within the end cap. The two balance to provide a muffler function.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.